1. Field of the Invention
The invention relates to a circuit arrangement for recirculating the energy produced during the braking of electric motors into a supply system. Preferred areas of application for devices of this type include the drives of machine tools and textile, printing and other machines for which frequent starting up and braking is characteristic.
2. Description of the Related Art
Devices for recirculating the energy produced during the braking of electric motors are known in the art. One such device is described in “Unidrive Regen Installation Guide, Issue No. 2” on the website http://www.controltechniques.com. This involves an adaptation of controlled direct current power supplies to other drives. The device is comprised of a power supply branch, which is made up of a voltage-controlled resistive circuit that is connected to the power supply system and an HF filter, a forward branch and a reverse branch. An electric motor is connected to the output side of the forward branch. The forward branch comprises a rectifier, an intermediate circuit and an inverter. The output terminals of the intermediate circuit are also connected via a blocking diode to the reverse branch, which comprises a second inverter and an adapting circuit with a line filter, said adapting circuit being connected via one choke per phase, and an isolating transformer, which is connected to the power supply branch. The isolating transformer effects the galvanic separation of the reverse branch from the supply system, thereby preventing the creation of high circulating currents. However, the isolating transformer has a relatively high volume and represents a major cost factor.
The object of the invention is therefore to implement the feeding of the energy that can be obtained during the braking of electric motors to the supply system without the use of an isolating transformer.